1. Chapter 18.2b
The Digestive System

2. Organs of the Digestive System
There are 2 parts of your digestive system – the digestive tract and the accessory organs.
The organs of your digestive tract is the mouth, esophagus, stomach, small intestine, large intestine, rectum, and anus.
The accessory organs are the tongue, teeth, salivary glands, liver, gallbladder, and pancreas. These are important in mechanical and chemical digestion. Liver, gallbladder, and pancreas produce and store enzymes to break down food.
Organs of the Digestive System

3. Mechanical digestion starts in the mouth with chewing food and mixing it with your tongue.
Chemical digestion starts with the addition of saliva in the mouth.
As you chew your tongue moves food around and mixes it with saliva.
After you chew your food and start breaking it down in your mouth you swallow it and the food passes into your esophagus.
The Mouth

4. When food moves in the esophagus it passes over the epiglottis
When food moves in the esophagus it passes over the epiglottis. This is a structure that covers your windpipe to prevent food from entering it.
The esophagus is a muscular tube that is about 25 cm long. It takes 4 to 10 seconds for food to move down the esophagus to the stomach.
No digestion takes place here.
The food moves by peristalsis – waves of muscle contractions.
The Esophagus

5. The Stomach The stomach is a muscular bag.
Mechanical and chemical digestion takes place here. Mechanically, food is mixed in the stomach by peristalsis. Chemically, food is mixed with enzymes and strong digestive solutions to break the food down.
Special cells in the stomach releases 2 L of hydrochloric acid solution each day. This solution digests food and it also keeps bacteria out that were in food.
The food is changed into chime this is a thin, watery liquid. This will move out of the stomach into the small intestine.
The Stomach

6. The small intestine is small in diameter but measures 4 to 7 meters in length. The first part of the small intestine is called the duodenum. Most digestion takes place here. A fluid from your liver is added (called bile). Bile breaks up large fat particles.
Absorption takes place in the small intestine. There are many villi here – these are fingerlike projections. They increase surface area so more nutrients can be absorbed.
The Small Intestine

7. When what has not been absorbed moves from the small intestine it goes into a large intestine. The large intestine absorbs water from undigested material. The remaining materials becomes more solid and eventually passes out of the body.
The Large Intestine

8. Bacteria Are Important
Many types of bacteria live in your body. Bacteria lives in the digestive tract. The bacteria in your large intestine feeds on undigested material and make vitamins you need..
Bacteria Are Important